CLIVAR features AER research on subpolar North Atlantic Ocean decadal variability

The subpolar North Atlantic (SPNA) Ocean shows pronounced changes in temperature from one decade to the next. Such decadal temperature fluctuations in the SPNA are strongly correlated with other components of the climate system, for example, Atlantic hurricane activity, North American and European river flow, and rainfall over the African Sahel and northeast Brazil. Understanding the nature and predictability of decadal variability in SPNA temperatures has thus been a major goal in climate studies, and various hypotheses have been submitted to explain this decadal variability apparent in climate models and data records.

Over the last two decades, there has been a dramatic shift in oceanic climate over the SPNA: while there was a strong warming of the SPNA during 1994-2004, there has been a marked cooling of the region during the more recent 2005-2015. To better understand the nature of this event, AER scientists Drs. Christopher Piecuch, Rui Ponte, and Christopher Little – along with colleagues from George Mason University and NASA’s Jet Propulsion Laboratory – considered an ocean circulation model constrained to most available ocean data. They found that, in the model, the striking SPNA decadal trend reversal from 1994-2004 to 2005-2015 arose largely from variable heat transports by the ocean’s midlatitude horizontal gyre circulation. What’s more, these fluctuations in the model’s ocean gyre circulation were strongly correlated with the local surface wind field. These results imply that predictability of SPNA decadal variability is intimately tied to the predictability of the overlying atmosphere.

For more details, see the CLIVAR press release here, or the full peer-reviewed research article here.